Abstract: A prefabricated wall insert unit is disclosed for rapid installation in a wall having an outer surface, an internal space, a ceiling plate, and a floor support. When installed, an exterior assembly, with upper and side perimeter attachment areas, projects away from the outer wall surface. A header is fastened to the exterior assembly proximate the upper perimeter attachment area and is within the wall internal space immediately below the ceiling plate. At least two side support members are fastened to the upper support member and to the exterior assembly proximate the side perimeter attachment areas. When installed in the wall, the header and each said side support member are within the wall internal space and each side support member extends from the header to proximate the wall floor support.